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Solve #862 and #864: bode_plot phase wrapping incorrect for multiple systems #863

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Merged
merged 5 commits into from
Feb 18, 2023
Merged

Solve #862 and #864: bode_plot phase wrapping incorrect for multiple systems #863

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b6769f6
Solve #862: bode_plot phase wrapping incorrect for multiple systems
henklaak Feb 17, 2023
2afd397
Fix wrap
henklaak Feb 17, 2023
f990f40
PEP8 requires lowercase variable name
henklaak Feb 17, 2023
f2878d5
Don't plot in tests...
henklaak Feb 17, 2023
4c4b3fc
Fix regression with matplotlib 3.7.0
henklaak Feb 17, 2023
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28 changes: 17 additions & 11 deletions control/freqplot.py
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Original file line number Diff line number Diff line change
Expand Up @@ -276,18 +276,21 @@ def bode_plot(syslist, omega=None,
if initial_phase is None:
# Start phase in the range 0 to -360 w/ initial phase = -180
# If wrap_phase is true, use 0 instead (phase \in (-pi, pi])
initial_phase = -math.pi if wrap_phase is not True else 0
initial_phase_value = -math.pi if wrap_phase is not True else 0
elif isinstance(initial_phase, (int, float)):
# Allow the user to override the default calculation
if deg:
initial_phase = initial_phase/180. * math.pi
initial_phase_value = initial_phase/180. * math.pi
else:
initial_phase_value = initial_phase

else:
raise ValueError("initial_phase must be a number.")

# Shift the phase if needed
if abs(phase[0] - initial_phase) > math.pi:
if abs(phase[0] - initial_phase_value) > math.pi:
phase -= 2*math.pi * \
round((phase[0] - initial_phase) / (2*math.pi))
round((phase[0] - initial_phase_value) / (2*math.pi))

# Phase wrapping
if wrap_phase is False:
Expand Down Expand Up @@ -1021,9 +1024,11 @@ def _parse_linestyle(style_name, allow_false=False):
# Plot the scaled sections of the curve (changing linestyle)
x_scl = np.ma.masked_where(scale_mask, resp.real)
y_scl = np.ma.masked_where(scale_mask, resp.imag)
plt.plot(
x_scl * (1 + curve_offset), y_scl * (1 + curve_offset),
primary_style[1], color=c, **kwargs)
if x_scl.count() >= 1 and y_scl.count() >= 1:
plt.plot(
x_scl * (1 + curve_offset),
y_scl * (1 + curve_offset),
primary_style[1], color=c, **kwargs)

# Plot the primary curve (invisible) for setting arrows
x, y = resp.real.copy(), resp.imag.copy()
Expand All @@ -1041,10 +1046,11 @@ def _parse_linestyle(style_name, allow_false=False):
# Plot the regular and scaled segments
plt.plot(
x_reg, -y_reg, mirror_style[0], color=c, **kwargs)
plt.plot(
x_scl * (1 - curve_offset),
-y_scl * (1 - curve_offset),
mirror_style[1], color=c, **kwargs)
if x_scl.count() >= 1 and y_scl.count() >= 1:
plt.plot(
x_scl * (1 - curve_offset),
-y_scl * (1 - curve_offset),
mirror_style[1], color=c, **kwargs)

# Add the arrows (on top of an invisible contour)
x, y = resp.real.copy(), resp.imag.copy()
Expand Down
12 changes: 12 additions & 0 deletions control/tests/freqresp_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -375,6 +375,18 @@ def test_phase_wrap(TF, wrap_phase, min_phase, max_phase):
assert(max(phase) <= max_phase)


def test_phase_wrap_multiple_systems():
sys_unstable = ctrl.zpk([],[1,1], gain=1)

mag, phase, omega = ctrl.bode(sys_unstable, plot=False)
assert(np.min(phase) >= -2*np.pi)
assert(np.max(phase) <= -1*np.pi)

mag, phase, omega = ctrl.bode((sys_unstable, sys_unstable), plot=False)
assert(np.min(phase) >= -2*np.pi)
assert(np.max(phase) <= -1*np.pi)


def test_freqresp_warn_infinite():
"""Test evaluation warnings for transfer functions w/ pole at the origin"""
sys_finite = ctrl.tf([1], [1, 0.01])
Expand Down